Analysis of Basic Hazard Parameters Before and After the February 6, 2017 Ayvacik Earthquake (Mw=5.4)

The Biga Peninsula, which has the most complex tectonic segments of the northwestern Aegean region, shows a remarkable dense seismicity. The earthquake hazard analysis of medium and large earthquakes occurred at differ-ent periods for the peninsula and its vicinity is the basis of this study. The basic earthquake parameters those are generally known as a and b-values, were determined, and evaluated for the earthquakes M> 2 during the instrumental period earthquake catalog, which is the database of this study. A homogenous earthquake catalog combined of two institutions COMU and KOERI data, which are quite dense and have high solution quality, play a remarkable role in this study. It was observed that the dense seismic activity after the earthquake that initiated in the event of Mw = 5.4 on February 6, 2017, especially in Ayvacik and its close vicinity, and which has been continuing, was clustered around Tuzla deformation zone in an area of approximately 25x10 km. Probabilistic parameters including b-value which can be related with local tectonic structures and stress states before and after this earthquake were also evaluated. In the short and long term, the decreasing and increasing tendencies of these parameters before and after the main shock were examined spatially and temporally in addition to local and regional dominant stress-es, heterogeneity in the upper crust and the contribution of the geothermal resources to the seismicity and seism tectonic structure. Considering the spatial density of earthquakes towards to Saroz-Ayvacik-Edremit, the pre-earthquake b-values increased inversely with the stresses, and then this decline in behavior was distinguished in the 2014 and 2017 earthquake sequences